Bone anchor system

ABSTRACT

A bone anchor system anchors a support member to a bone. The bone anchor system comprises a body having a shank adapted for insertion into a hole in the bone. A head is formed on the shank. The head has a support engagement portion adapted to secure the support member to the body. A passage extends from an entry point to an exit point formed in the body. An expandable member has a flexible wall at least partially enclosing an anchoring chamber. The expandable member has an expanded state configured to conform to a cavity in the bone. The anchoring chamber is in fluid communication with the exit point. The expandable member is adapted to expand when a filler material is provided into the anchoring chamber. A portion of the expandable member conforms to the cavity and the body and the support member are substantially anchored to the bone.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.11/870,978, filed on Oct. 11, 2007, now U.S. Pat. No. 7,789,901 theentire disclosure of which is incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to surgical anchors for securing support membersto bone, and more particularly, to bone anchor systems for securing asupport member to a vertebra.

BACKGROUND OF THE INVENTION

Skeletal structures are formed of bones and adjoining structures whichinclude cartilage, for instance. These skeletal structures may requireartificial support or stabilization. For example, the human spine iscomposed of a column of thirty-three bones, called vertebrae, and theiradjoining structures. Most of the vertebrae are capable of individualmovement and generally are connected by anterior and posteriorlongitudinal ligaments. An intervertebral disc is positioned betweenopposing faces of adjacent vertebrae. Each of these vertebrae include avertebral body and a dorsal-arch that enclose an opening, called thevertebral foramen, through which the spinal cord and spinal nerves pass.Unfortunately, there are numerous diseases that deteriorate one or moreportions of the vertebra or disc. As a result, nerves may be pinchedcausing enormous pain. In these and other situations, surgicalinstallation of various devices is designed to reduce pain to allow theperson to resume a normal life.

One well-known device for spine stabilization procedures is the pediclescrew which is threaded for engagement with bone. A pedicle screw issurgically installed posteriorly into and through a pedicle. A supportmember such as a plate, semi-rigid member, flexible member, or rigid rodis attached to the pedicle screw for stabilization of the spine. If thethreaded portion of the screws do not properly secure to the bone, thepedicle screw will loosen and pull out or break. This loosening canoccur over time. Securing the pedicle screw is even more problematicwhen the bone, particularly cancellous bone, is diseased, deteriorating,or degenerating. For instance, when a pedicle screw is used onosteoporotic patients, the lack of bone density makes it difficult toproperly engage the pedicle screw threads within the pedicle resultingin a fragile connection between the pedicle screw and bone.

Therefore, a bone anchor system with improved fixation to bone that doesnot require screwing into bone and where the external load is dispersedto other load bearing structures in contact with bone is needed.

SUMMARY OF THE INVENTION

The invention provides a bone anchor system for anchoring a supportmember to a bone. The bone has a hole formed therein and a cavity formedat a distal end of the hole. The bone anchor system comprises a bodyhaving a shank that has a proximal portion and a distal portion adaptedfor insertion into the hole. A head is formed on the proximal portion ofthe shank, and has a support engagement portion adapted to secure thesupport member to the body. A passage extends from an entry point formedat the proximal portion to an exit point formed in the distal portion.The bone anchor system further comprises an expandable member having aflexible wall at least partially enclosing an anchoring chamber, and anexpanded state configured to conform to the cavity. The distal portionof the shank cooperates with the expandable member and the anchoringchamber is in fluid communication with the exit point. The expandablemember is adapted to expand when a filler material is provided into theentry point, passes through the passage, passes out of the exit point,and into the anchoring chamber. Upon filling the anchoring chamber withthe filler material, a portion of the expandable member conforms to thecavity and the body and the support member are substantially anchored tothe bone.

The invention further includes a method for securing a support member toa bone. The method comprises forming a hole in the bone, removingadditional bone at a distal end of the hole to form a cavity, insertingthe bone anchor system into the hole, and providing a filler materialinto the entry point to the anchoring chamber to fill and thereby expandthe anchoring chamber of the expandable member within the cavity. Uponfilling the anchoring chamber with the filler material, a portion of theexpandable member conforms to the cavity, and the body and the supportmember secured thereto are substantially anchored to the bone. [0007] Inanother embodiment, the bone anchor system includes a first body and asecond body, each having the shank, the head, and the passage, and theexpandable member is a tubular member having a first opening, a secondopening, and the anchoring chamber therebetween. For this embodiment,the method comprises forming a first hole through a first pedicle into avertebra, forming a second hole in a second pedicle into the vertebra,and then removing additional bone to form a cavity connecting the firsthole with the second hole. The second opening of the tubular member isinserted into the first hole, through the cavity, and out of the secondhole to position the first opening adjacent the first hole, the secondopening adjacent the second hole, and the anchoring chamber within thecavity. The shank of the first body is inserted into the first openingof the tubular member and into the first hole. The shank of the secondbody is inserted into the second opening of the tubular member and thesecond hole. The filler material is provided to at least one of thepassages of the first and second bodies and into the anchoring chamberto fill and thereby expand the anchoring chamber of the tubular memberwithin the cavity. Upon filling the anchoring chamber with the fillermaterial, a portion of the expandable member conforms to the cavity andthe first body, the second body and the support member securedtherebetween are substantially anchored to the vertebra.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description given below, serve to explain the invention.

FIG. 1 is side elevation view of a spine having two bone anchor systemsinserted into adjacent vertebra with a support member secured at eachend by the adjacent bone anchor systems;

FIGS. 2A and 2B are cross-sectional views of the spine of FIG. 1 takenalong section line 2A-2A, showing one embodiment of the bone anchorsystem having an expandable member in an unexpanded state and in anexpanded state, respectively, inserted into both the first and secondpedicles;

FIG. 3 is a cross-sectional view of one embodiment of the bone anchorsystem with the expandable member in an unexpanded state;

FIGS. 4A and 4B are cross-sectional views of another embodiment of thebone anchor system having a threaded portion in threaded engagement withbone with the expandable member in an unexpanded state and an expandedstate, respectively;

FIG. 5 is a cross-sectional view of the spine of FIG. 1 taken alongsection line 2A-2A, showing another embodiment of the bone anchor systemhaving an expandable member in an expanded state;

FIG. 6 is a partial cross-sectional view of another embodiment of thebone anchor system having a projection extending from the body forengagement with bone; and

FIGS. 7A, 7B, and 7C are cross-sectional views of FIG. 6 taken alongsection line 7A-7A, showing other embodiments of the projection.

DETAILED DESCRIPTION

FIGS. 1-3 depict an exemplary bone anchor system 10 according to theprinciples of the present disclosure. The bone anchor system 10facilitates anchoring a support member 12 to a bone 14. In oneembodiment, as shown in FIG. 1, two bone anchor systems 10 secure thesupport member 12 between adjacent vertebral bodies 14. By way ofexample, the support member 12 may be a combination of spacer, forinstance SULENE®-PCU, and cord, for instance SULENE®-PET, that iscurrently a part of the DYNESYS® Dynamic Stabilization System availablefrom Zimmer Spine, Edina, Minn. In other applications, the supportmember 12 may be a rigid member such as a rod or a plate, a semirigidmember, a flexible member, or another member adapted to be anchored tobone.

While the embodiments illustrated in the figures depict the bone anchorsystem 10 for anchoring the support member 12 to a vertebral body 14,one skilled in the art will observe that the bone anchor system 10 maybe used to attach a variety of other support members to other bones, inboth humans and nonhumans. Due to its configuration, subsequent loadingof the support member 12 may not loosen or break the bone anchor system10 as is known with prior art threaded bone anchors, pedicles screws andthe like. Additionally, the construction of the bone anchor system 10can conform to a void existing within the bone 14. This void may bepreexisting in bone-like osteoporotic bone or created by a surgeon asdescribed below. Furthermore, the bone anchor system 10 can be easier toinstall. In one exemplary embodiment as shown, for example, in FIG. 2A,the bone anchor system 10 does not require screwing a device into thebone 14. Yet, in contrast with the prior art, the bone anchor system 10can be implanted directly into a hole created in the pedicle, canprovide greater stability, and may provide improved fixation of thesupport member 12 to the bone 14.

With reference to FIG. 3, the bone anchor system 10 includes a body 16and an expandable member 18. The body 16 has a head 20, a shank 22, anda passage 24. The head 20 has a support engagement region 26 forsecuring the support member 12 to the body 16. The support engagementregion 26 may be, for instance, similar to a polyaxial top-loading head,known in the art. The shank 22 has a proximal portion 28 proximate tothe head 20 and a distal portion 30 opposite the head 20. The passage 24extends from an entry point 32 formed in the head 20, through the shank22, and exits at an exit point 34 in the distal portion 30. AlthoughFIG. 3 illustrates the passage 24 in the center of the shank 22, thepassage 24 may be a channel or passage along the outer surface that canreceive a filler material via a delivery tube (not shown). By way ofexample and not limitation, the body 16 may be made of titanium or oneof its alloys, stainless steel, TRABECULAR METAL™ material sold byZimmer Spine, Inc. of Edina, Minn., or other biocompatible materialsuitable for biological use.

The expandable member 18, as shown in FIG. 3 in an unexpanded state,cooperates with the shank 22. In one embodiment, the expandable member18 matches the profile of the body 16 to aid in insertion into bone. Theexpandable member 18 has a flexible wall 36 that at least partiallyencloses an anchoring chamber 38. Therefore, the anchoring chamber 38 isin fluid communication with the passage 24. By way of example, theexpandable member 18 may be a metallic, woven fabric made of titanium orone of its alloys, stainless steel; a polymeric material, such aspolymethyl methacrylate (PMMA); or other biologically compatible metalssuitable for biological use. In one embodiment, the expandable member 18may be a conforming member that conforms to the shape of a void in bone.

FIGS. 2A and 2B depict an exemplary embodiment of a pair of bone anchorsystems 10, for example, one bone anchor system 10 for anchoring to afirst pedicle 40 and a second for anchoring to a second pedicle 42. InFIG. 2A, each of the expandable members 18 is shown in an unexpandedstate with one bone anchor system 10 shown prior to insertion into ahole 44 formed in the vertebral body 14 with a cavity 46 formed at adistal end of the hole 44. To further illustrate the placement of thebone anchor system 10 in the bone 14, a second bone anchor system 10 isalso shown in FIG. 2A. The second bone anchor system 10 is positioned ina second hole 48 and a second cavity 50 has been formed at the distalend of the second hole 48. While two bone anchor systems 10 are shownand described, a single bone anchor system 10 may be used to secure thesupport member 12 to the bone 14. In FIG. 2A each of the bone anchorsystems 10 are inserted into their respective holes 44, 48 withoutrelative rotation, i.e. no screwing is required. As will be describe inmore detail later, in an alternative embodiment, a portion of the body16 can include threads at the proximal portion 28 of the shank 22designed to engage the pedicle 40, with the distal portion 30 being freeof threads. In yet another alternative embodiment, a portion of the body16 can include generally longitudinally formed projections or ribs thatengage the pedicle 40 possibly stabilizing the body 16 against torque.

The holes 44, 48 may be formed by hand with a tool or machined, such asby drilling with a drill, into the bone 14 or by other methods known inthe art. The cavities 46, 50 may also be formed by similar methods. Inone exemplary embodiment, at least one dimension of each cavity 46, 50is larger than the diameter of the respective hole 44, 48.

Now with reference to FIG. 2B, the expandable members 18 of each boneanchor system 10 are shown in an expanded state. In accordance with theprinciples of the present disclosure, following insertion of the boneanchor system 10 into the hole 44, as described previously and shown inthe FIG. 2A, a filler material 52 is provided into the passage 24. Thefiller material 52 passes through the passage 24 into the anchoringchamber 38 to expand the expandable member 18. As the anchoring chamber38 fills, for example, by injecting the filler material 52 therein, theflexible wall 36 may contact the surface of the cavity 46. While theexpandable member 18 may be entirely filled with the filler material 52such that the flexible wall 36 conforms to the cavity 46, it will beappreciated that partially filling the anchoring chamber 38 may alsofacilitate fixation of the bone anchor system 10 to the bone 14. By wayof example and not limitation, the filler material 52 may include bonecement or in situ curable polymeric materials including, for example,elongated polymeric materials, polymeric beads, hydrogel materials,fusion promoting materials, autograft bone, allograft bone, xenograftbone, or any combination thereof. Furthermore, other desired materialsincluding bioresorbable materials, may include poly(lactic acid),poly(glycolic acid), p-dioxanon fibers, polyarylethyl, polymethylmethacrylate, polyurethane, amino-acid-derived polycarbonate,polycaprolactone, aliphatic polyesters, calcium phosphate, unsaturatedlinear polyesters, vinyl pyrrolidone, polypropylene fumarate diacrylate,or mixtures thereof, or other biocompatible compounds.

In an exemplary embodiment, a flowable and curable filler material 52fills and expands the expandable member 18 and hardens in vivo. As shownin FIG. 2B, once the expandable member 18 is expanded such that one ofits dimensions is greater than a diameter of the hole 44, for example,the expandable member 18 will have an interference fit with the hole 44and can conform to the cavity 46. Thus, the expandable member 18 willresist loads that act to pull the body 16 longitudinally from the hole44 by transferring those loads to the bone 14 over a larger area thanprior art bone anchors, pedicle screws and the like. For similarreasons, the bone anchor system 10 also resists lateral forces that mayact to loosen it to a greater degree than prior art devices. While FIGS.2A and 2B depict the cavities 46, 50 having a generally circular crosssection, one skilled in the art will observe that the cavities 46, 50may have a variety of shapes and sizes. In any case, when the fillermaterial 52 expands the expandable member 18, the expandable member 18may conform to the cavity 46 with the flexible wall 36 abutting thesurface of the cavity 46 to create an interference fit between theexpandable member 18 and the hole 44, as previously mentioned.

With reference now to FIGS. 4A and 4B, another exemplary embodiment ofthe bone anchor system 10 is depicted. As shown, the shank 22 has ahelical thread 54 on a threaded portion 56 between the proximal portion28 and the distal portion 30. Thus, the surgeon may screw the body 16into the bone 14. The threaded portion 56 frictionally engages the bone14 surrounding the hole 44 as the surgeon rotates the body 16. Inaddition, to further stabilize and support the body 16 and supportmember 12, the surgeon may introduce the filler material 52 into theexpandable member 18, as shown in FIG. 4B. A cannula 58 may be insertedat least partially into the passage 24 to introduce the filler material52 into the passage 24 to expand the expandable member 18 with thecavity 46. Once the filler material 52 is in the anchoring chamber 38,it may begin hardening. In this embodiment, the passage 24 can be usedas a cannulated delivery mechanism in conjunction with a guide wire (notshown) for percutaneous delivery of the bone anchor system 10. Inanother embodiment, a wire can be inserted in the passage 24 to engagethe expandable member 18 and maintain the expandable member 18 in aconfiguration that allows for filling with the filler material 52.

In another exemplary embodiment, as shown in FIG. 5, a bone anchorsystem 60 includes a first body 62 and a second body 64. Each of thebodies 62, 64 may be similar such that they each have a shank 66, a head68, and a passage 70. Alternatively, only one of the bodies 62, 64 mayinclude a passage 70. An expandable member 72 cooperates with both thefirst and the second bodies 62, 64 through a first and second openings74, 76 in a flexible wall 78. Thus, in one embodiment the expandablemember 72 has a tubular configuration. The flexible wall 78 at leastpartially encloses an anchoring chamber 80. Once the expandable member72 is inserted and at least partially filled, the anchoring chamber 80may have, for example, a u-shape. The anchoring chamber 80 may preventlongitudinal withdrawal of either or both bodies 62, 64 from theirrespective holes 44, 48. As one skilled in the art will observe andappreciate, in addition to transferring loads to the bone 14 surroundingthe expandable member 72, any loads acting to withdraw the bone anchorsystem 60 may be distributed to other portions of the bone anchor system60, such as from the first body 62 to the second body 64 or vice versa.

As previous mentioned and with reference now to FIGS. 6, 7A, 7B, and 7C,the body 16 may include one or more ribs or projections 94 extendingtherefrom. As shown in FIG. 6, the projections 94 are generally formedalong the shank 22 between the proximal portion 28 and the distalportion 30 and project radially from the body 16. The projections 94 maysufficiently engage the bone 14 and thus prevent rotation of the body 16therein when a torque is applied to the body 16 via the supportengagement region 26, for example. While FIG. 6 depicts the projections94 as extending along the shank 22 from the proximal portion 28 toproximate the distal portion 30, one skilled in the art will observethat even discrete (i.e. those extending less than the length of theshank 22) projections extending radially from the body 16 to engage thebone 14 may prevent rotation of the body 16. FIGS. 7A, 7B, and 7C areexamples of cross sections of exemplary projections 94. It will beappreciated, however, that the projections 94 may have many otherconfigurations.

As shown best in FIGS. 3, 4A, and 4B, in other exemplary embodiments,the expandable member 18 is secured to the shank 22 by a securing system82 such as a clamping system. The securing system 82 may ease handlingof the bone anchor system 10 by preventing the expandable member 18 frominadvertently falling off the shank 22 prior to insertion into the hole44. Also, the securing system 82 may prevent the body 16 from beingaccidentally withdrawn from the expandable member 18 during or followinginflation but prior to the filler material 52 hardening. Moreover, thesecuring system 82 may enhance the stability of the bone anchor system10 by providing additional interfacial support between the body 16 andthe expandable member 18 even after the filler material 52 has hardened.In one embodiment, a sheath 83 that is more rigid than the expandablemember 18 can be provided over the expandable member 18 that maintainsthe shape and position of the expandable member 18 on the body 16. Thesheath 83 may include a mechanism that allows removal of the sheath 83after placement of the bone anchor system 10.

In an exemplary embodiment, as shown in FIG. 3, the securing system 82may, for example, frictionally secure the expandable member 18 to theshank 22. In this embodiment, the shank 22 is formed with a recess 84. Acompression ring 86, having generally the same shape as the recess 84,captures the flexible wall 36 within the recess 84. The ring 86 may besized and shaped to apply compressive loads to the flexible wall 36 toenhance the frictional forces that secure the flexible wall 36 withinthe recess 84. In one embodiment, the compression ring 86 engages theshank 22 adjacent to the proximal portion 28 making the securing system82 accessible after the body 16 is inserted into the bone 14.

FIGS. 4A and 4B illustrate another example of a securing system 82. Inthis embodiment, the threaded portion 56 has a longitudinal annularrecess 88. The longitudinal annular recess 88 may be formed between aportion of the shank 22 and a sleeve 89 and extend from the distalportion 30 toward the proximal portion 28. The longitudinal annularrecess 88 cooperates with the flexible wall 36 of the expandable member18 such that the flexible wall 36 may be inserted into the longitudinalannular recess 88. For example, the flexible wall 36 may be placedaround the shank 22 and the sleeve 89 may slide over the flexible wall36 into a position proximate the shank 22 to clamp or otherwisefrictionally engage the flexible wall 36. In addition, when the shank 22is inserted into the bone 14, the threaded portion 56 threadably engagesthe bone 14, which may compress the sleeve 89 onto the flexible wall 36,thus clamping the expandable member 18 within the longitudinal annularrecess 88. In another embodiment, the distal portion 30 may taper towarda distal end 92 to facilitate insertion of the bone anchor system 10into the hole 44. As with the previously described securing system 82,the longitudinal annular recess 88 may prevent separation of theexpandable member 18 from the body 16 before, during, and afterexpansion of the anchoring chamber 38, as well as, prior to hardening ofthe filler material 52.

With reference to FIG. 3, in another embodiment, the shank 22 is formedhaving a crown and fluke configuration 90. The crown and flukeconfiguration 90 are formed at the distal portion 30 of the shank 22. Asshown in FIG. 2B, the crown and fluke configuration 90 submerge in thefiller material 52 when the anchoring chamber 38 is filled with thefiller material 52. In this embodiment, when the filler material 52fully expands the expandable member 18, and in the use of an in situcurable filler material 52 that fully hardens, the crown and flukeconfiguration 90 facilitate capturing of the body 16 within the fillermaterial 52 essentially anchoring the body 16 within the filler material52 against loads tending to withdraw the body 16 from the bone 14. Withreference to FIGS. 4A and 4B, in another embodiment, the exit point 34is formed at the distal end 92 of the shank 22 and one or more otherexit points 35 branch from the passage 24 in the distal portion 30proximal to the distal end 92. It will be appreciated that when theexpandable member 18 is filled to capacity with the filler material 52,and residual filler material 52 “backs up” into the exit point 34 andother exit points 35 and into the passage 24, the body 16 may be morerigidly secured against forces acting on the body 16 due to theadditional contact surface area created by the exit points 34, 35 andthe filler material 52.

In another exemplary embodiment, best shown in FIG. 3, the shank 22 isformed with the crown and fluke configuration 90 formed on the distalend 92, and the exit point 34 is formed proximal to the distal end 92.Thus, when the filler material 52 flows through the passage 24 and outthe exit point 34, the filler material 52 may flow over and around thecrown and fluke configuration 90. In an event where the expandablemember 18 is less than fully expanded, or when the bone anchor system 10is oriented such that the filler material 52 flows away from the distalportion 30, the filler material 52 will be more likely to remain incontact with the crown and fluke configuration 90 and, consequently, maybe more likely that the filler material 52 may, in the case of an insitu curable filler material, hardens around the crown and flukeconfiguration 90. Thus, making it more likely that loads distributed tothe body 16 will be transferred directly to the filler material 52rather than from the body 16 to the expandable member 18 and then to thefiller material 52.

Similar to the method of installing the bone anchor system 10 shown inFIGS. 2A and 2B, in another embodiment a method of securing a supportmember 12 to a bone 14 comprises forming the first and the second holes44, 48 into the bone 14 such that the holes 44, 48 are in fluidcommunication, as shown only in FIG. 5. As one skilled in the art willappreciate, the holes 44, 48 may be formed whereby they intersect, oradditional bone at the distal portion of the holes 44, 48 may be removedto connect the holes 44, 48. In any case, once two holes 44, 48 areconnected, expandable member 72 may be inserted through one hole 44 andout the other 48. The first and second bodies 62, 64 are inserted intothe first and second openings 74, 76 in an arrangement as shown in FIG.5. It will be appreciated that the present disclosure is not limited toany particular order in which the first and second bodies 62, 64 isinserted into the bone 14. For instance, in one exemplary method, theexpandable member 72 is inserted into one hole 44 and out of the secondhole 48. Following insertion of the expandable member 72, the firstopening 74 remains accessible in the first hole 44 and the secondopening 76 remains accessible within the second hole 48. Therefore, thefirst and second bodies 62, 64 may be inserted into their respectiveopenings 74, 76 and, consequently, into their respective holes 44, 48.

In another embodiment, one body 62 may be secured to the expandablemember 72 between the recess 84 and the ring 86 of the securing system82 of FIG. 3. One end of the expandable member 72 may then be insertedinto the hole 44 followed by insertion of the body 62 into the hole 44.The other end of the expandable member 72 is pulled out of the secondhole 48. At this point the expandable member 72 may be trimmed to lengthnear the surface of the pedicle 40 prior to inserting the second body 64into the second hole 48 and possibly clamping the expandable member 72to the second body 64. One skilled in the art will observe that thereare a number of different orders that the expandable member 72 and thefirst and second bodies 62, 64 may be inserted into their respectiveopenings 74, 76 and holes 44, 48.

Once the expandable member 72 and the first and second bodies 62, 64 areinserted into the holes 44, 48, the filler material 52 may be providedto the expandable member 72 through the passage 70 or a second passage71 and into the anchoring chamber 80. One skilled in the art willobserve that introducing the filler material 52 through one passage 70may allow air or other gasses within the expandable member 72 to bedisplaced out of the second passage 71 by the incoming filler material52. In other embodiments, the filler material 52 may be provided intoboth passages 70, 71 substantially simultaneously.

While the present invention has been illustrated by the description ofone or more embodiments thereof, and while the embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention is therefore not limited to thespecific details, representative apparatus and process and illustrativeexamples shown and described. Accordingly, departures may be made fromsuch details without departing from the scope of the general inventiveconcept.

1. A bone anchor system for anchoring a support member to a bone havinga cavity formed therein, the system comprising: a body having a proximalend portion, a distal end portion and a longitudinal axis extendingtherebetween; a deformable member attached to the distal end portion ofthe body, the deformable member being deformable upon expansion from anunexpanded configuration to an expanded configuration in which thedeformable member is spaced apart from the distal end portion of thebody, the deformable member expanding in a radial direction; a sleevefor attaching the deformable member to the body, the sleeve configuredsuch that when the deformable member is placed over the body, the sleeveslides over and frictionally engages the deformable member, therebyretaining the deformable member between the body and the sleeve; and ahead region at the proximal end portion of the body, the head regionhaving a support engagement channel extending through the head in adirection transverse to the longitudinal axis, the support engagementchannel configured to receive a support member.
 2. The system of claim1, further comprising a passage extending from an entry point in thehead region to an exit point in the distal end portion.
 3. The system ofclaim 2, wherein the exit point is in fluid communication with thedeformable member, whereby the deformable member is adapted to expandwhen a filler material is provided into the entry point, passes throughthe passage, passes out of the exit point, and into the deformablemember, thereby expanding at least a portion of the deformable member toconform to the bone cavity and anchor the system to the bone.
 4. Thesystem of claim 1, wherein the deformable member includes a flexiblewall configured to conform to the bone cavity in the expandedconfiguration, thereby defining an anchoring chamber between the distalend portion of the body and the flexible wall.
 5. The system of claim 1,further comprising a plurality of threads on the body forming a threadedportion between the proximal end portion and the distal end portion. 6.The system of claim 1, further comprising an expansion tool configuredto expand the deformable member.
 7. The system of claim 6, wherein theexpansion tool is a cannula configured for insertion into the passage todeliver a filler material.
 8. The system of claim 1, further comprisinga support member releasably attached to the head region.
 9. The systemof claim 1, wherein the deformable member comprises a metallic fabric.10. A bone anchor system for anchoring a support member to a bone havinga cavity formed therein, the system comprising: a body having a proximalend portion, a distal end portion and a longitudinal axis extendingtherebetween; a deformable member attached to the distal end portion ofthe body, the deformable member being deformable upon expansion from anunexpanded configuration to an expanded configuration in which thedeformable member is spaced apart from the distal end portion of thebody, the deformable member expanding in a radial direction; a sleevefor attaching the deformable member to the body, the sleeve configuredsuch that when the deformable member is placed over the body, the sleeveslides over and frictionally engages the deformable member, therebyretaining the deformable member between the body and the sleeve; and ahead region at the proximal end portion of the body, the head regionhaving a support engagement region adapted to receive a support member,the support engagement region configured to allow polyaxial movement ofthe body relative to the support member.
 11. The system of claim 10,wherein the support engagement region includes a channel extendingthrough the head region in a direction transverse to the longitudinalaxis.
 12. The system of claim 10, wherein the head region comprises apolyaxial top-loading head.
 13. The system of claim 10, wherein the bodyhas a passage extending from an entry point in the head region to anexit point in the distal end portion.
 14. The system of claim 13,wherein the exit point is in fluid communication with the deformablemember, whereby the deformable member is adapted to expand when a fillermaterial is provided into the entry point, passes through the passage,passes out of the exit point, and into the deformable member, therebyexpanding at least a portion of the deformable member to conform to thebone cavity and anchor the system to the bone.
 15. The system of claim10, wherein the deformable member includes a flexible wall configured toconform to the bone cavity in the expanded configuration.
 16. A methodof securing a fixation member to a bone, comprising: preparing a hole ina portion of bone; providing an expandable support device comprising: abody having a proximal end portion, a distal end portion and alongitudinal axis extending therebetween; a deformable member attachedto the distal end portion of the body, the deformable member beingdeformable upon expansion of the expandable support device from anunexpanded configuration to an expanded configuration in which thedeformable member is spaced apart from the distal end portion of thebody, the deformable member expanding in a radial direction, wherein thedistal end portion of the body includes a sleeve for attaching thedeformable member to the body; and a head region at the proximal endportion of the body, the head region having a support engagement channelextending through the head in a direction transverse to the longitudinalaxis, the support engagement channel configured to receive a fixationmember; placing the deformable member over the distal end portion of thebody, sliding the sleeve over the deformable member, whereby the sleevefrictionally engages the deformable member, thereby retaining thedeformable member between the body and the sleeve; inserting theexpandable support device into the hole such that the body anddeformable member are inside the hole and the head region remainsoutside the hole; expanding the expandable support device within thehole; and attaching a fixation member to the head region of theexpandable support device.
 17. The method of claim 16, wherein the bodyhas a passage extending from an entry point in the head region to anexit point in the distal end portion, and the deformable member includesa flexible wall, wherein the exit point is in fluid communication withthe deformable member, whereby the deformable member is adapted toexpand when a filler material is provided into the entry point, passesthrough the passage, passes out of the exit point, and into thedeformable member.
 18. The method of claim 17, wherein the step ofexpanding the expandable support device within the hole includesinserting a filler material through the passage and into the deformablemember, thereby expanding at least a portion of the deformable member toconform to the hole and anchoring the expandable support device in thehole.